Muffler with return bend tuning passage



Dec. 6, 1966 W. H. POWERS I. MUFFLER WITH RETURN BEND TUNING PASSAGEOriginal Filed April 2, 1956 Dec. 6, 1966 W. H. POWERS 3,289,786

MUTFLEN WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956B'Sheets--Sheet 2 Dec. 6, 1966 w. H. POWERS MUFFLER WITH RETURN BENDTUNING PASSAGE 8 Sheets-Sheet 5 Original Filed April 2y 1956 INVENTGR/7/ 70 we 75 ffa nm -QN Dec. 6, 1966 W. H. POWERS 3,289,786

\ MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1955 8Sheets-Sheet 4 /rf l 1074 INVENTOR. M1/fer )9x/wens Dec. 6, 1966 w. H.POWERS 3,289,786

MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956 8Sheets-Sheet 5 Dec. 6, 1966 w. H. POWERS MUFFLER WITH RETURN BEND TUNINGPASSAGE 8 Sheets-Sheet G Original Filed April 2, 1955 IN VEN TOR. H we7s y ,ff

Dec. 6, 1966 w. H. Fowl-:Rs

MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2L 1956 BSmets-Sheet '7 i NVENTOR. //d//er /7/ F0 wens* @me 70W/wsu@ Dec. 6, 1966W. H. POWERS 3,289,786

MUFFLER WITH RETURN BEND TUNING PASSAGE Original Filed April 2, 1956 8Sheets-Sheet 8 NN nl WN NN H N Nm United States Patent O 3,289,786MUFFLER WITH RETURN BENI) TUNING PASSAGE Walter II. Powers, Jackson,Mich., assignor to Walker 3 Claims. (Cl. 181-54) This application is a`division of U.S. Serial No. 136,287 filed September 6, 1961 (nowabandoned) which in turn is a division of U.S. Serial No. 575,404, filedApril 2,1956 (now abandoned).

This invention relates to muier constructions and, in particular, tomuiers of the type .adapted to silence the exhaust stream of automotiveinternal combustion engines.

It is .the object of this invention to provide a muflier constructionthat may be economically manufactured and yet which is rugged anddur-able in construction and which will efficiently silence the powerfulmodern day automotive engines, particularly those having automatictransmissions, without appreciable back pressure.

The invention accomplishes this and other objects by means of aconstruction in which theY gas passages within the ymuffler casing arearranged in a tri-How pattern and subjected to the .action of `a numberof spit chambers both large and small which will remove the roughnessand high frequency sounds. The gases and sounds lare'also exposed to theaction of a number of resonator chambers which will act to :remove thelower frequency heavy power notes. The internal tri-flow construction isof such a nature that it can be preassembled; that is, prepared as asubassembly and then inserted into the mutller casing. The lover-alldesign is such as t-o meet the cost and performance requirements ofautomotive manufacturers, particularly those manufacturing V-S engines.

The invention is illustrated in modified forms in the accompanyingdrawings in which:

FIGURE 1 is a longitudinal section ot a preferred form of the inventionas taken on line 1-1 of FIG. 3;

FIG. 2 is an end View taken from the left of FIG. 1;

FIG. 3 is a cross section taken along the line 3-3 of FIG. l, thelouvers being omitted for simplification;

FIG. 4 is a side elevation of the gas conduits with parts broken away toshow the structure of the louvers in the tube;

FIG. 5 is a cross section through the louvers shown in FIG. 4 and llaidout straight rather than on the curved contour of the tube;

FIG. 6 is a longitudinal cross section through -a slightly modified typeof muiiier, the end view and sectional view being the same for thisrnuiiier as FIGS. 2 and 3;

FIG. 6A is a section on line 6A-6A of FIG. 6;

FIG. 7 is a longitudinal section through the front end of a muiilersomewhat similar to the muffler shown in FIG. 6, lthe structure in FIG.7 revealing a pancake inlet arrangement;

FIG. 8 is a section on line `8--8 of FIG. 7;

FIG. 9 is a view showing =a .modied arrangement for forming the trifiowpassages in the muier, this constituting a pancake arrangementconsisting of complemental stampings which when iitted together willdefine the spit chambers around the outermost passages and define the.inner passage itself;

FIG. 10 is a longitudinal cross section of a modified form of mutlier;

FIG. 11 is an end view taken from the inlet side of the muler of FIG.10;

FIG. 12 is a cross section taken along the line 1212 of FIG. 10i;

nr' ICC FIG. 13 is a longitudinal section through another muffierembodying the invention;

FIG. 14 is an end elevation taken rom the inlet end of'the muie'r ofFIG. 13;

FIG. l5 is an end elevation taken from the outlet side of the muiiier ofFIG. 13;

FIGS. 16 and 17 are cross sections taken -along .the lines 16--16 and17-17 respectively of FIG. 13;

FIG. 18 is a longitudinal section through another form of mutiierembodying the invention;

FIG. 19 is an end view from the inlet end of the muffler of FIG. 18;

FIGS. 20 and 21 are cross sections taken along the lines 2li-20 and21-21 of FIG. 18;

FIG. 22 is a longitudinal section through another muffler embodying theinvention;

FIG. 23 is an end elevation taken at .the inlet end of the muiiier;

FIG. 24 is an end elevation taken at the outlet side of the muflier; and

FIGS. 25 and 26 are cross sections taken along the lines 25-25 and 26-26of FIG. 22.

Considering iirst the muiler 1 that is shown in FIGS. 145, there is acasing 3 of oval cross sectional form constructed in accordance withknown practice so that inten nal bailes or partitions can be spot weldedto it. It is provided with a head 5 at the inlet end and a head 7 at theoutlet end, both heads being interlocked as shown at 9 with the ends ofthe casing 3. An inlet bushing 11 is expanded as shown lat 13 int-o -atight contact with the outwardly turned flange or neck 15 on the head 5so that the bushing 11 can be properly spot welded to the neck after thehead and internal pa-rts have been assembled with the casing 3. The head7 has an outwardly turned neck or flange 17 in which is fitted an outletbushing 1-9 that is expanded diamet-rically into -contact with `the neck17 as shown at 21 so that the bushing 19 can be spot welded to theilange 17 after the head and internal parts have been assembled to thecasing 3. Gas to be silenced Hows from the engine through a suitableexhaust line into the inlet bushing 11 and passes through the variousgas silencing apparatus within the casing 3 and out through the bushing19 to the tail pipe of the exhaust system.

The central part of the apparatus within the muffler 1 is a subassembly23 which can be 'manufactured as a unit and inserted in the muier, thevarious other parts being assembled later on from both ends of theInuiiier and then the heads 5 and 7 attached by interlocking at 9 to thecasing after which the bushings 11 and 19 are expanded at 13 and 21,respectively, into contact with the necks 15 and 17 and spot welded inplace. The subassembly 23 is supported by the parallel transversepartitions 25 and 27. These have flanges 25a and 27a. that -run parallelto ythe inside surface of the casing 3 and which are turned outwardly sothat they can be spot welded to the casing ,3 by suitable spot weldingapparatus including inner and outer electrodes that are radially alignedinside and outside of the casing, the outwardly turned flangespermitting such apparatus to be inserted inside the casing in yproperposition. The partition 25 has three outwardly turned flanges or necks29, 30, and 31 which are aligned, respectively, with the outwardlyturned anges o-r necks 4on partition 27 that are designated by referencenumbers 32, 33, .and 34 respectively. Spot welded in position to thenecks 29 and 32 is an intermediate tube 35 having louvers 37 formedtherein ralongvthe surface which are of the type shown in FIGS. 4 and 5so tha-t they can direct gas circumferentially around t'ne outside ofthe t-ube 35. Mounted in `and spot welded to the necks 30- and 33 is lanoutlet tube 39 and this projects some distance beyond the end of thepartition 27 as shown at 41. Mounted in and spot welded to the necks 31and 34 is the inlet tube 43 and this tube has a.

somewhat enlarged en-d projecting toward the inlet end from thepartition 25 as will be seen at 45. The tubes 39 and 43 each havelouvers 37 of the type already rnentioned. The inlet tube 43 has a pairof spit chambers 47 and 48 formed .around it and the intermediate passtube 35 has spi-t chambers 49 and 51 formed a-round it.

The chambers 47 and 48 as well as the chambers 49 and 51 are formed bypancake assemblies 53 and 55 respectively. The pancake assemblies 53 and55 are substantially identical so that the description of one willsufce. Each assembly consists of a pair of identical stampings or halves52 which are provided with flanges 57 that lie in the plane of theoriginal sheet metal from which the pancake halves were originallyformed, the chamber portions being pressed or bowled out of the atpieces. The flanges 57 are joined together face to face as clearly seenin FIG. 3 and spot welded together so that the two halves form a shellaround the tube. The ends 59 and 61 of the halves of the pancake areformed to snugly t the periphery or semi-periphery of the tube as is thecenter portion 62. These can be spot welded to the tubes if desired.Angularly spaced from the flanges 57, the halves of the pancakeassemblies 53 and 55 are formed with flats as shown at 65 and one edgeof the pancake assembly is trimmed so that the ange 57 is removed beyondthe diameter of the spit chambers as will be seen at 67 in FIG. 3. Byremoving the flange 57 at the point 67 and forming the flats 65 it ispossible to tit the pancakes 53 closely to the contour of the casing 3and to get a good deal of additional space adjacent the center outlettube 39 as is evident from FIG. 3. The pancake assembly halves are soformed that they can be considered standard parts to be used in muler 1or in various other mulers having different over-all dimensions andinternal spacings. The ats 65 and the cut oif outer flanges increase theflexibility in this respect because they reduce the space taken up bythe pancakes, enabling them to be used in mufllers Where quarters aremore cramped than in muffler 1.

It will be seen that the partitions 25 and 27 with the tubes 35, 39 and43 spot welded in the respective necks and in turn carrying pancakeassemblies 53 and 55 can all be assembled as a subassembly into a spotwelded integral unit. This unit 23 can then be inserted into the centerportion of the casing 3 whereupon the partitions 25 and Z7 can be spotwelded in place to the casing and, after this, the elements to the leftand to the right of the subassembly 23 can be inserted into the muffleras a part of the nal assembly operation. When inserting assembly 23 Iprefer to put the casing 3 in a fixture that will hold the casing in itsproper shape and I also prefer to outwardly flare the ends of the casingso that the assembly 23 will in effect be funneled into it. These stepswill eliminate diiculties caused by having the outwardly turned flangeson partitions 25 or 27 as the leading edge during insertion.

Adjacent to but spaced longitudinally toward the inlet end of the muferis a transverse partition 71 and spaced between it and the header 5 isanother transverse partition 73. The partitions 71 and 73 have inwardlyand outwardly turned flanges or necks 75 and 77, respectively, throughwhich extends a connecting inlet pipe 79, with louvers 37 therein, thatslidably ts within the enlarged end 45 (flared at 83) of the tube 43(which is a part of the subassembly 23) as will be seen at the point 81.The outermost end of the tube 79 is spot welded at 85 to the inner endof the inlet bushing 11. It will be seen that this arrangement providesa reinforcement for the head 5 since the bushing 11 is spot welded tothe head and then to the tube 79 which in turn is spot welded to thepartitions 73 and 71 by way of necks 77 and 75.

The chamber between the head 5 and the partition 73 constitutes aresonator chamber 87. The chamber 89 between the partition 71 and thepartition 25 is a cross'over chamber. Connecting the cross-over chamberS9 with the resonator chamber 87 is a tuning tube 91 that is spot Weldedin and to inwardly and outwardly turned flanges or necks 93 and 95,respectively, in the partitions 71 and 73.

At the outlet end of the casing 3 there is a transverse partition 97that is spaced from the partition 27 to define therewith a cross-overchamber 99. Between the partition 97 and the head 7 is a partition 101which like the partition 97, and the other partitions herein, has anoutwardly extending ange running around it by means of which it isheated in position on the inside of the casing 3 and then spot welded tothe casing by radial electrodes on the inside and outside of the casing.The space between partition 97 and partition 101 constitutes a resonatorchamber 103 while the space between the partition 101 and the end header7 constitutes another resonator chamber 105. The outlet bushing 19 iitsin an outwardly turned flange or neck 107 in the partition 101 and isspot Welded to it, thus tying the head 7 to the partition 101 toreinforce the head 7. As shown at 109, fitting inside of the end of thebushing 19 and spot welded to it is a connecting tube 111 that isenlarged at its end as shown at 113 and flared so that it slip ts overthe end 41 of the outlet passage tube 39, the tube 111 extending throughthe inwardly flanged neck 115 of the partition 97 and being spot weldedto it. A tuning tube 117 is spot welded to inwardly and outwardly turnedflanges 119 and 121 on partitions 97 and 101 and is preferably alignedwith tube 43. Flanged opening 123 connects chambers 103 and 105 to forma compound resonator.

In assembly, after unit 23 has been inserted and spot welded in place,the partitions 71 and 97 with tubes 91, 111, and 117 already spot weldedto flanges 93, 115, and 119 are inserted and the outwardly turnedpartition flanges spot welded to the casing by spot welding apparatusinserted through the ends of the casing. Partition 73 with tube 79 spotwelded to flange 77 (and bushing 11 spot welded to tube 79) andpartition 101 with bushing 19 spot welded to flange 107 are theninserted, the outwardly turned flange slipping readily over tube 91 andthe ared end of bushing 19 slipping over the end of tube 111. Then, fromthe inside of the casing, the outwardly turned partition flanges arespot welded to the casing, the tubes 91 and 117 are spot welded tooutwardly turned flanges 95 and 121, and the end 109 of tube 111 is spotwelded to bushing 19. It may be noted that end louvers 37 Will engagepartition 71 to limit the slipping of tube 79 into tube 43 and that ange75 will catch under flare 83 to control insertion of partition 71. Itmay also be noted that the tubes 79 and 43 may be connected together, ifdesired, in the same sort of joint as bushing 19 and tube 111, i.e., thetube 43 slipping inside and spot welded to tube 79 which in turn wasspot welded to flange 75. After the partitions and members have beeninserted and spot welded in place, as described, the end headers 5 and 7may be interlocked at 9 and the bushings 11 and 19 expanded and spotWelded to flanges 15 and 17.

In operation, gas enters the inlet bushing 11 and flows through the tube79 into the tube 43. Some of the gas passes through the louvers 37 oftube 79 into the large spit chamber 121 between partitions 71 and 73.Other gas passes through louvers 37 of the tube 43 into the spitchambers 47 and 48, these various spit chambers acting to eliminateroughness and relatively high frequency sounds. Gas leaving the tube 43enters the cross-over chamber 99 and passes upwardly to the intermediateowback tube 35. Heavy notes may pass through the imperforate tube 117into the resonator chamber 105 and this action is compounded by means ofthe flanged tuning neck or opening 123 in partition 101 which connectsthe resonator chamber in a compound relationship with the resonatorchamber 103. The gas that is flowing through the tube 35 is subjected bymeans of its louvers 37 to the high frequency spit chamber control ofchambers 49 and 51 and flows into the cross-over chamber 89. Heavy notesstill in the gas may pass through the imperforate connecting tuning neck91 into the resonator or tuning chamber 87. The gas ilows toward theoutlet through the tube 39 and from louvers 37 into the spit chamber ofrelatively large size 125 which lies between the partitions 25 and 27.The gas flows through tube 39 into the tube 111 and thence into theoutlet bushing 19 from which it goes to the tail pipe and to theexhaust.

It may be noted that aligned apertures 124 in the headers and partitionsare drain holes and may be formed at the bottom of all six internalpartitions and preferably, for standardization, also at the tops thereofas shown. When all the internal partitions are provided with the drainopenings 124, which are preferably about 1A diameter, water within themuffler will flow back and forth lengthwise of the mulller from the coolto the hot chambers as the muffler rocks back and forth slightly due tomovement of the vehicle in which it is mounted. This water will be`vaporized by the hot exhaust gases and carried out by them without theneed for any external drainage openings. The end chambers 87, 121, 103and 105 tend to run cooler than the other central chambers and act asnatural condensers but due to the lconnection of these chambers with thehotter central chambers by way of openings 124 the condensate will moveto the central chambers and be evaporated, thus markedly reducingcorrosion of the mulller. These features are of particular importance indual mulller systems as the mulllers therein tend to be cooler and thusmore likely to corrode.

Turning now to the form of mulller shown in FIG, 6, this mulller beingdesignated by the reference number 141, it will be seen that there isfound within the casing 143 of the mulller a subassembly which isidentical to the subassernbly 23 and which will therefore be identifiedby the reference number 23', no further details of structure beingmentioned since it is interchangeable with the unit 23 that has alreadybeen described. At the inlet end of the mufller 141 are a pair oftransverse partitions 145 and 147. The partitions have inwardly andoutwardly turned necks 149 and 151, respectively, vthrough which extendsan imperforate tuning neck or tube 153 which is spot welded to both ofthe necks 149 and 151, being spot welded to neck 149 outside of thecasing and to neck 151 inside the casing in accordance with assemblytechniques discussed above. The partitions 147 and 145 also have flangedopenings or necks 155 and 157 and through these extends a long inlettube 159. The tube 159 is spot Welded to the neck 157 and projectsbeyond the partition 145 as shown at 161. It also projects a verysubstantial distance beyond the partition 147 toward the inlet of themufller as shown at 163. The tube 159 may be of a lock seam constructionand provided with spaced embossments 165 whereby it is readily turnedinto a tubular section from a ilat section and spot welded to the neck157 on the embossments prior to being inserted in the casing. The tube159 is provided with a set of louver openings similar to thosepreviously described and shown in FIGS. 4 and 5, these being identifiedby reference number 167 and omitted from FIG. 6A for simplicity. Thelouvers 167 are located between the partitions 145 and 147 and open intothe chamber dened by these partitions, this constituting a large spitchamber 169 and louvers 16'7a abut partition 145. Outwardly of theembossment 165 area, the tube 159 is provided with another set ofsimilar louvers 171. Around the tube and around the set of louvers 171is a pancake construction 173 of the same type as previously describedpancakes 55 and consisting of complemental hal-Ves 175, as shown in FIG.6A. The halves are flat sheet metal pieces bowled out and spot weldedtogether around their flanges 176 to provide a spit chamber 177. Theclosely fitting ends 175a of the pancakes are spot welded to the tube159. One ilange 176' is cut off llush with the periphery, as before, sothat it fits snug against the casing. The halves are provided with flats174 to decrease over-all size as indicated in connection with pancakes55.

A flanged partition 181 at the inlet end has a flanged tuning neck oropening 183 that is larger than the tube 159 and the inlet bushing 185which is spot Welded to the tube 159 at 187.

The partition 181 also has flanged openings 189 and 191. The spacebetween the partitions 181 and 147 coustitutes a resonator chamber 193and the space between the partition 181 and the inlet end header 195constitutes another resonator chamber 195 which, being in series withthe chamber 193, the two chambers act as a compound resonatorconstruction. The header 195 is assem-l bled to the casing 143 after theparts already described have been inserted in accordance with principlesoutlined above and is interlocked as shown at 197 with the ends of thecasing. The header 195 has an outwardly flanged neck 199 that is largerthan the inlet bushing 185 so after assembly the bushing 185 is expandedas shown at 201 into tight engagement with the neck 199 and then it canbe spot welded to the flange or neck 199. j

At the outlet end of muiller 141 there is a dished partition 203 whichhas a ilanged neck or opening 205 in which is spot welded imperforatetuning tube 207 prior to insertion in the casing. The space between thepartition 203 and the partition 27 constitutes a cross-over chamber 209.Also spot welded to a neck 211 in the partition 203, prior to insertionin the casing, is the inlet bushing 213 and it will be seen that it sliplits over the projecting end 41' of the outlet passage tube 39. Theoutlet end header 215 can be placed over the bushing 213 and theperiphery thereof interlocked at 197 with the end of the casing. Thebushing 213 can then be expanded at 217 into tight contact with the neck219 of the header 215 and spot welded to it. It will be seen that fromthis arrangement the inlet bushing 185 and the outlet bushing 213 bothact to tie their respective headers 195 and 215 to the internal parts ofthe mufller and thus serve to reinforce the heads against strain orblowout.

In operation, inlet gas enters the bushing 185 from the exhaust line ofthe engine and passes along tube 159 into the tube 43. As the gas passesthe spit chamber 177 (in resonator chamber 193) certain of the highfrequency sounds and roughness are removed. When it passes the largerspit chamber 169 some of the lower frequency roughness and noise isremoved by passage through the louvers 167. In the tube 43 the gas issubjected to the action of spit chambers 47' and 48. Gas leaving thetube 43 enters the cross-over chamber 209 and some of the lower noisemay pass through the imperforate tuning neck 207 which is in alignmentwith the intermediate tube 43' and be subjected to the action of theresonator chamber 221 which lies between the partition 203 and the endheader 215. Gas passing through the intermediate passage 35 is subjectedto the action of the spit chambers 49' and 51 and then passes into thecross-over chamber 223 between the partition 25 and the partition 145.Gas in the cross-over chamber 223 is subjected t6 the action of thecompound resonator chamber construction 193 and 195, the gas or soundwaves passing through the tube 153 into the chamber 193 and from thenceit can pass through the openings 183, 191, or 189 into the chamber 195,it of course being obvious that anything entering these chambers must bereflected back to the cross-over chamber 223 through the tuning tube153.

VIn order to leave the cross-over chamber 223 for the eX- haust line,the gases must pass through the outlet pipe 39' and in doing so theywill be subjected to the action of the large spit chamber 125. Gas thenenters the outlet bushing 213 and passes onto the tail pipe and thenceto atmosphere.

FIGS. 7 and 8 show a modified form of inlet end construction for amuiller 141', similar to mulller 141 as shown in FIG. 6, in which tuningoccurs olf thek inlet tube 159. In this arrangement there is animperforate 7' transverse partition 251 and a transverse partition 253having a flanged opening or slot 255, a necked large opening 258, andsmaller openings 257 which communicate the chamber 259 :between thepartitions with the chamber 261 between the inlet header 195' and thepartition 253, The partition 253 is of the particular shape that is seenbest in FIG. 8. The inlet tube section 159 has a long series of louvers263 preferably similar to those shown in FIGS. 4 and 5, these beingomitted from FIG. 8 for simplicity. Supported on and around the inlettube 159 is a pancake construction 265 which consists of the stampedidentical halves 267 and 268 formed from initially at sheet metal. Theflanges are intermediate web 269 and 271, respectively, of the halvesare spot welded together to form a unitary section and the end necks 273and 274 are spot welded to the tube in the manner that has already beendiscussed above in connection with the pancakes used to provide the spitchambers. The halves .are formed to provide a long split chamber 275around the openings 263. Communicating with the spit chamber 275 is afairly long tuning passage 277 (constituting with chamber 275 a longreverse bend passage) which lears gases from the spit chamber into theresonator chamber 259 where the gases are subject-ed to the tuningaction of chambers' 259 and 261. The construction will serve in someapplications to replace tuning from the crossover chamber 223 in themuliier of FIG. 6. The llange 269 is cut off on one side as shown at269' to provide a snug lit to the side of the casing. The pancake 265 issupported by spot welding of the necks 273 and 274 on the tube 159 andalso by spot welding of anged slot 255 thereto at points of contact 279.Partitions 251 and 253, tube 159', and pancake 265 may be put togetheras a subassembly and inserted into the casing prior to interlocking ofhead 195. Obviously the structure shown in FIGS. 7 and 8 could bemodilied to include an inlet bushing expanded onto neck 199 and spotwelded to tu'be 159 just as in FIG. 6, if desired.

FIG. 9 shows a modified pancake construction 301 for the subassembly 23or 23'. In this arrangement the outlet passage 39" as well as the spitchambers 47, 48 49, and 51" are all formed in the two complementalpancake stampings 303 and 305 which are spot welded together in thecontacting lianges and webs 307 and 309. The spit chambers are neckeddown in the same manner as before to contact and be spot welded to tubes35" and 43". The outlet passage 39" formerly provided by tubes 39 or 39is, in this case, formed right in the halves 303 and 305. Louvers 37 forpassage 39 lare formed in the halves 303 and 305. It is obvious thatpancake 301' can be combined with partitions 25 or 27 (or 25 and 27') toform a spot lwelded su-bassembly 23 having the advantages and functionsalready described.

FIGS. -12 show another muier 401 embodying the principles of thisinvention. This muiiier has an outer shell or casing 403 consisting of aspirally wrapped double ply inner shell 402 which is interlocked at 405to the inlet and outlet end headers 407 and 409 and around which isdisposed a single layer 404 of sound deadening metal which is attachedin place after the partitions have been spot welded to the doublewrapped shell 402, the friction between the two layers ldissipatingsound energy. Disposed within the casing 403 is a tri-ow subassembly 23awhich corresponds to the unit 23 that has already been described, theprincipal difference being that pancake spit chamber are provided aroundonly one of the three tubes. The subassembly 23a comprises inlet andoutlet side partitions 411 and 413 having three sets of aligned openingsall of which are provided with outwardly extending flanges 415, 417, and419. Spot welded in the sets of flanges are the inlet tube 421, theintermediate tube 423, and the outlet tube 425. Each of the tubes isprovided with louvers, the tubes 423 and 425 having louvers 427 whichare more or less tubular shaped while the tube 421 has louvers 429 thatare shaped like the en a louvers 37 of FIGS. 4 and 5. Mounted on thetube 421 around the louvers 429 is a double pancake assembly 431identical to those already described in connection with the othermodifications and which provides a pair of spit chambers 433communicating with the inlet tube 421.

Between the subassembly 23a and the inlet header 407 is a transversepartition 435 having an outwardly turned flange whereby it may be spotwelded to the casing after insertion of the subassembly 23a. Thepartition 435 has a central opening provided with an outwardly extendingange 437 and this is aligned with the flange 439 around the inlet in theheader 407. An inlet bushing 441 extends through the outwardly extendingflange 439 and is spot welded to it. The inlet bushing is necked down at443 and ared at its inner end as shown at 445 so that it slidablyreceives the outer end of the inlet tube 421 which is spot welded atassembly to it, the ange 437 and the bushing 441 also being spot weldedtogether at a pre-assembly operation (i.e. before the parts are insertedin casing 403). The partition 435 also has a tuning tube 447 spot weldedto the liange 449 of an opening therein which is aligned with tube 423,this being done prior to insertion of the partition 435 in the mufflercasing. The partition 435 divides the space between partition 411 andheader 407 into a resonator chamber 451 and a cross-over chamber 453.

On the outlet side of the subassembly 23a are three partitions455, 457,and 459, all provided with outwardly extending flanges so that they may:be spot welded to the casing after insertion therein. The partition 455has an opening aligned with the outlet tube 425 and provided with aninwardly extending flange 461 to which is spot welded the -outlet tube463. The outlet tube 463 is also spot welded in a neck 465 formed in theoutlet header 409 and it slidably tits in a flanged opening 466 inpartition 457 and extends through an enlarged opening 467 in thepartition 459. The tube 463 is enlarged at its inner end and flared toslidably lit over the end of the tube 425 at assembly, the outwardlyflared end engaging the ange 419 to control the location and insertionof the tube 463.

Aligned with the inlet tube 421 is a tuning tube 468 that is spot weldedat a pre-assembly operation to the flange 469 in partition 455 and afterassembly to the outwardly ange 470 of partition 457, the outer end ofthe tube 463 terminating in but being spaced from the flanged edges ofan opening 471 in the partition 459. The partitions 455, 457, and 459dene with the partition 413 and the outlet header 409, a series ofchambers which in FIGURE l0 are from left to right as follows: acrossover chamber 472, a large spit chamber 473, a resonator chamber474, and a resonator chamber 475 which is compounded with the resonatorchamber 474 through the openings 467 and 471 in the partition 459 aswell as by a flanged opening 476 in partition 459 (the anged openings inthe partition 459 acting as tuning necks). Louvers 477, similar tolouvers 37, in the tube 463 open into the spit chamber 473.

The opposite sides of the muli-ler casing 403 may, in the region ofchambers 451 and 475, be provided with inwardly extending embossments orbeads 478 to prevent iutter of the side walls and the inlet bushing 441may have a pair of indentations 479 formed therein on opposite sides asstops for the pipes to be inserted therein.

In operation of the muiiier 401, gases enter the inlet bushing 441 andpass through the tube 421 where some of the higher frequency sounds aresilenced in spit chambers 433. Some of the gas passes through the tube468 where lower notes are silenced in the resonator chambers 474 and 475but this gas must return through the tube 468 and with gas from theoutlet of the tube 421, enter crossover chamber 472 and reverse itsdirection to pass through tube 423 wherein additional silencing isaccomplished by communication through louvers 427 with the large spitchamber 400 between the partitions 411 and 413, some back pressurereducing cross bleeding occurring from tube 423 to outlet tube 425through chamber 480. Gas leaving the tube 423 enters cross-over chamber453 and communicates through rtuning tube 447 with a resonator chamber451 where further low notes may be removed. From cross-over chamber 443gas passes rearwardly through tube 425 and out of the muiiiler throughthe bushing 465 after additional silencing in spit chambers 480 and 473takes place through communication with these chambers by way of louvers427 and 477,

To permit condensed water to ow to the relatively hot chambers 472, 453,and 480 the six partitions in the muffler 401 are provided with small(14 diameter) drain holes at their midplane at the top and bottomthereof as seen at 481 in FIG. l2, the inlet and outlet headers 407 and409, however, being imperforate. This arrangement provides for internaldrainage of water that accumulates inside the casing 403 so that the hotgases passing through the muiller will evaporate the water and pick upthe resulting vapor and carry it out yof the muiiier.

FIGS. 13-17 show another modied form of muffler 501 using a tri-iiowsubassembly 23h similar to the assemblies already described. Thismuflier has a casing 503 t-o the opposite ends of which are interlocked,after insertion of all the inner parts, the inlet and outlet headers 504and 505, respectively. The subassembly 23h comprises the inlet sidepartition 506 and the outlet side partition 507 each of which haveoutwardly turned peripheral flanges whereby they may be spot welded inplace in the casing 503 after insertion. The partitions 506 and 507 havesets of aligned holes provided with outwardly extending iianges as shownat 508 and 509 to which are spot welded the inlet tube 510 and thereturn ow tube 511, respectively. The tubes 510 and 511 have rows oflouvers 512, 513 formed therein opening into the charnber 514 :betweenpartitions 506 and 507. The partition 506 has a central opening providedwith an outwardly turned iiange 515 to which is spot welded the end ofan outlet tube 516. The outlet tube 516 has three sets of louvers 517,518, and 519 all of which are similar to louvers 37. The louvers 51S and519 are encased by a pancake subassembly 520 of the type alreadydescribed in detail which forms small volume spit chambers 521 and 522around the outlet tube, the louvers 517 opening directly into therelatively large volume chamber 514. The pancake 520 projects throughthe double diameter neck 523 formed in partition 507 and which has ashape best seen in FIG. 17, the at sides of the pancake being paral--lel to at sides of the opening.

On the inlet side of the subassembly 23h are two partitions 524 and 525each of which has an outwardly turned ange so that it may be spot weldedto the casing 503 after it has been inserted therein. The partition 525has an inwardly extending flange 526 around an opening that is alignedwiththe outlet tube 516 and to which is spot welded the inner end of atuning tube 527 prior to insertion of the partitioin 525 in the casing.The outer end of the tube 527 is supported on and spot welded atassembly to the flange 528 in the partition 524. The partition 525 alsohas an inwardly turned flange 529 around an opening that is aligned withthe inlet tube 510 and to this ange is spot welded, prior to assembly,an inlet tube 530. The tube 530 is necked down at 531 and flared at itsinner end so that it can readily slide over the projecting end of thetube 510. The tube 530 is provided with two sets of louvers 532, similarto louvers 37, and these open into spit chambers 533 provided around thetube 530 by the pancake assembly 534 of the type already described. Theouter end of the tube 530 extends through a tuning neck 535 of largerdiameter than the tube and over its outer end is slipped the end oftheinlet bushing 536 which is spot welded to the tube 530 on the outside ofthe header 504 as indicated -at 537, the bushing 536 having been spotwelded to an inwardly flanged neck 538 on the head 504 at a pre-assemblyoperation. The partitions 524 and 525 act with the inlet header 504 andthe 10 partition 506 to define the chambers 540 and 541 which act as acompound resonator chamber connected by tube 527 with the cross-overchamber 542. Another tuning neck 543 is formed in partition 524 to actwith the neck 535 to intercommunicate the chambers 540 and 541.

At the outlet side of the subassembly 23h is a partition 544 with anoutwardly turned flange so that it may be spot welded to the casingafter insertion therein. This has an opening aligned with the outlettube provided with an outwardly extending ilange 545 in which are seatedthe embossments 546 formed on the outlet tube 516 and which embossmentsare spot welded to the ange 545 at assembly. The outer end of the outlettube 516 is enlarged as seen at 547 and spot welded to the outlet neck548 formed integrally in the outlet header 505. The partition 544 actswith the outlet header 505 to provide a spit chamber 549 thatcommunicates with the outlet tube 516 through louvers 550, similar tolouvers 37, in the outlet tube. It acts with the partition 507 to deiinea lcross-over chamber 551 connecting the inlet tube 510 and theintermediate tube 511.

In operation, exhaust gas enters the inlet bushing 536 and passesthrough the inlet tube 530 wherein certain high frequency noisesandroughness are removed by the spit chambers 533. In passing through theinlet tube 510 additional noise is removed yin the large spit chamber514 by passage through louvers 512. The gas leaving tube 510 enterscross-over chamber 551 and reverses direction to pass through tube 511back toward the inlet of the muier. During passage through tube 511certain noise and roughness is removed in chamber 514 by communicationtherewith through louvers 513. Gas leaving the tube 511 enters thecross-over chamber 542 and reverses direction to enter the outlet tube516. The gas in the cross-over chamber 542 and the outlet tubecommunicates with the compound resonator provided by chambers 540 and541 through the tube 527, which is aligned with the outlet tube 516, sothat heavy notes or low frequencies will be removed. Gas passing throughthe tube 516 passes by the louvers 517 which connects the gas withchamber 514. High frequencies and roughness still remaining in the gasare removed in spit chambers 521 and 522 and finally in spit chamber549.

It will be noted that the gas in cross-over chamber 551 4can communicatethrough a tuning neck 523 with the chamber 514 so that this chamber actsto some extent as a tuning chamber to remove tones or notes `by virtueof this connection and as a spit chamber to remove roughness and noiseby virtue of communication with the three tubes through louvers 512,513, and 517. It will also be seen that cross bleeding from tubes 510and k511 land chamber 551 to louvers 517 in outlet tube 516 will lowerback pressure.

Drain holes on opposite sides of each of the tive interior partitionsare provided as shown at 552 and these will give internal orinter-chamber drainage via the hot gases as already explained.Additionally, a very small hole 553 (1/16-13" diameter, preferably 3/32diameter) may be provided in the outlet header on the bottom side of themuflier to provide for external drainage, this hole being so small thatit does not affect the acoustic characteristics of the chambers withinthe muier, especially the chamber 549, (Le. acoustically the muiiiershell is substantially imperforate) but at the same time being largeenough to permit water to leak out of the muier when the muier is coldand there are no hot gases to evaporate the water.

Another modified form of muiiier 601 is shown in FIGS. 18-21 in which atri-iiow type subassembly 23C is preassembled and inserted as a unitinto the casing 603 prior to closing of the ends of the casing byinterlocking the inlet and outlet headers 605 and 606 to the ends of thecasing as shown at 607. The subassembly 23e` includes an inlet sidepartition 608 and an outlet side partition 609. The partition 608 hasthree openings formed ll l therein for the support of tubes, the flangesaround these openings being designated by the reference numerals 610,611, and 612, respectively. The partition 608 also has a series ofrelatively large and non-restrictive openings 613 formed therein. Thepartition 609 has three flanged openings to support tubes Which arealigned respectively with the anges 610, 611, and 612, these annularflanges being designated by the reference numerals 614, 615, and 616,respectively. Supported in and spot welded t-o the flanges 610 and 614prior to insertion of the subassembly 23C is an inlet tube section 617;spot welded to flanges 612 and 616 is an intermediate tube 618; and spotwelded to the flanges 611 and 615 is a combination tuning tube andoutlet tube 619. The tubes 617 and 618 have louvers 620, similar tolouvers 37, formed therein and these are covered by pancake units 621similar to those already described but which provide single spitchambers 622 around the tubes. The tube 619 has relatively large andunrestricted openings 623 formed in the rear portion thereof, the frontportion being imperforate.

On the inlet side of the subassembly 23C are the partitions 624 and 625each of which have outwardly extending peripheral flanges so that it maybe spot welded to the casing after insertion therein. The partition 625has three openings formed therein delined by the flanges 626, 627, and628. Spot welded to these flanges prior to insertion of the partition625 into the casing 603 are the short tuning tube 629, the long tuningtube 630, and an expanded tube 631, all of these tubes projecting tosome extent beyond the outlet side of the partition 625 and the tube 630being adapted to slide within the flared enlarged end 632 of the tube619 and the tube 631 being ared and adapted to slide over the end of thetube 617 when the partition 625 is inserted in place in the housing 603.The partition 624 has an outwardly extending flange 633 around anopening that slips over the tube 630 when the partition 624 is insertedin the casing after which the ange 633 is spot welded to the tube 630.Prior to such insertion the tube 629 is spot welded adjacent its outerend as shown at 634 to the tube 630. The partition 624 also has a neckedopening 635 which slips over tube 631 when the partition is put into thecasing 603.

Within the tube 631 is an inlet tube 636 which is illustrated as beingof the same diameter as the tube 617 and aligned with it. It will beobserved that the tube 636 has louvers 637 formed in it and these may besimilar to louvers 37 already described. However, the outer diameteracross the louvers 637 is no greater and preferably slightly less thanthe enlarged outer end section 638 of the tube 636 which slides within aportion 639 of tube 631 and is spot welded to such portion. The tube 631is expanded at 640 opposite the louver 637 to provide a spit chamber 641surrounding the tube 636 and coextensive with the louver 637. The innerend of the tube 631 is necked down at 642 to fit in the annular flange628 and be spot welded thereto in a pre-assembly operation as previouslyindicated. The inner end 643 of the tube 636 has a slide tit in theportion 642 and it will be apparent that the tube 636 can be inserted atassembly through the outer end of tube 631 and spot welded to theportion 639. The portion 639 may be spot welded to the inner end of theinlet bushing 644, the outer portion of which is radially expanded onboth sides of the flanged opening 645 in the inlet header 605 and spotwelded thereto. It will be noted that the use of the expanded outer tube631 in conjunction with the inner tube 636 provides an inexpensivemethod of forming a spit chamber of substantial length around the innertube and one which takes up somewhat less space than the pancakeassemblies illustrated hereinbefore. It is also capable ofstandardization so that it can be used in various mulfler At the outletend of the muffler 601 are the partitions 647 and 648 each withoutwardly turned flanges so that they may be spot welded in place to thecasing after insertion. The partition 647 has an inwardly extending 12ange 649 defining an opening in alignment with the tube 619 and spotwelded at a pre-assembly operation to the flange 649 is an outlet tubesection 650 which is necked down and flared at its inner end to slipover the end of tube 619. Over the outer end of tube 650 is slipped theinner end of a bushing 650e which is spot Welded to the flanged outletneck 651 on the outlet header 606. The tube 650 has a series of louvers652, similar to louvers 37, formed therein and mounted on the tube andbushing is a pancake assembly 653 which provides a spit chamber 654around the louvers. The pancake assembly 653 is similar to those alreadydescribed and extends through and is supported by a flanged opening 655in the partition 648, the shape of the opening 655 being best seen inFIG. 21. On the outlet side of the louvers 652 is mounted a restrictormember 656 in bushing 65001 which consists of a reversely bent tubesection, the outer portion of which is spot welded to the tube 650 at apre-assembly operation and the inner portion 657 of which reduces theeifective area of the outlet tube to serve with the tuning or resonatorchambers to help silence pulses and beats.

The partition 647 has an inwardly flanged opening 661 formed therein towhich is spot welded a tuning tube 662. The tube 662 extends through theoutwardly extending flange 663 of an opening in the partition 648.Partition 648 also has a tuning neck 664 formed therein.

In operati-on of the mutller 601, gas enters thev inlet bushing 644 andpasses through tube 636 where roughness -and high frequency noises vareremoved in the spit chamber 641. They are further removed during passagethrough tube sect-ion 617 in the spit chamber i622. On leaving the inlettube 617 the igases enter the cross-over chamber `671 between partitions609 and 647. In this cham-ber they communi-cate through tuning tube 662with a resonator chamber 673 between the outlet header 606 and thepartition 648 and also through tuning neck 664 with a resonator chamber674 between partitions 647 and 648, the chambers 674 and `673 thusacting as a compound resonator. Gases in cross-over chamber 671 reversedirection and pass through tube 618 wherein they are subjected to theaction of the spit chamber 622. On leaving tube 618 they enter across-over chamber 676 between the partitions 625 and 608. Gases y-inthe cross-over chamber 676 are subjected to the action of a resonatorchamber 677 between partitions 624 .and 625 thnough the tuning neck 629which .is offset from the axis of the tube 618. The gases in crossoverchamber 676 pass through the non-restrictive openings 613 into thechamber 678 between partitions 608 and 609 and from there throughnonrest-rictive openings 623 yinto the t-ube 619 from which they can owthrough tube 650 and restrict-or 657 to the outside of the muiler, beingsubjected to the action of spit chamber 654 on the way through the tube650. Gases in the tube 623 are also subjected to the action of theresonator chamber `68() between the inlet header 605 and the partitionl624 by means of the tube 630 and the front portion of the t-u'be 619.It will be observed that by providing openings 613 in the partition 608to Iget flow into the -outlet tube through the volume of chamber 678, itis possible to make the tuning tube, pr-ovided by a section of tube 619`added to the Itube 630, lof unusually long length. This enables lowfrequencies to be removed in a relatively short muffler.

FIGS. 22-26 show another form of muffler 701 having a casing 703 withthe ends in-terlocked at 705 with the inlet header 706 and the youtletheader 707. Within the casing 703 ,is a .subassembly 23d correspon-dingin most respects to the subassemblies of this type previously described.Thi-s subassembly includes an inlet side partition 708 and an outletside partition 709, Iboth 4having outwardly turned ilanges whereby theycan be spot welded to the casing after inserti-on. The partitions '708and 7 09 have .aligned openings defined by anges 710 in which is mountedan inlet tube section 711 which is spot welded yin the subassembly tothe flanges 710. The tube 711 is provided with louvers 712 opening xintothe chamber 7.13 between the partitions 708 and 709. The partition 708has an intermediate openin-g defined by a flange 714 in whi-ch issupported and spot welded the end of an outlet tu-be 715. The outlettube 715 has three .sets of louvers 716, similar to louvers 37, each ofwhich opens in'to a zspit chamber 717 forme-d by the pancake assembly7118 which is similar to the pancake assemblies already described. Thethirdunit of the pancake assembly extends through the inwardly turnedneck 719 of an opening in the partition 709, the shape of the neck 719being best seen in FIG. 26. The outer end of the pancake assembly 718extends linto a cross-over chamber 721 formed between the partition 709and-an imperforate partition 722 which has an outwardly turned llia-ngewhereby it can be spot welded t-o the shell after insertion. Partition'722 4has an Aannular ange 723 in which are seated the embossments 724that are .formed -on the tube 715' and which are spot welded totheflange at assembly. The tube 715 has a set of louvers 725, similar tolouvers 37, opening into `the chamber 726 between the partition 722` andthe outlet header 707, the chamber 726 thus being a spit chamber. Theend of the tube 715 is spot welded to the inside of the drawn outletnipple 727 on the outlet header 70-7.

On the inlet side of the subassenibly 23d are partitions 729 and 739each having out'wardlyturned danig/es so that they can .be spot weldedto the shell after insertion. The partition 739 has a central opening`defined by a arige 740 in which is spot welded -a tuning tube 741 'thatis somewhat larger than the outlet passage 715 but generally alignedwith it, though the laxes are offset from each other. The partition 739also has an opening define-d by the flange 742 in which is spot Weldedat pre-'assembly the inlet tube section 743, the end of the section 743being necked Kdown and flared to fit over the end of the tube 711 andabut .the ange 710 as seen in FIG. 22. The tube 743 has two .sets oflouvers 745 which open into the two split chambers 746 yfor-med 'by apancake assembly 747 of the type already described. The tube 743 extendswith substantial clearance through a tuning neck 749 in the partition729 and its outer end is supported in and spot welded to the end of aninlet bushing 751 which is expanded and spot welded to the outwardlyturned flange 743 of the inlet header 706. The partition 729 has anoutwardly turned tiange 755 which at assembly tits over .the end of thetube 741 and is spot welded to it.

In operation of the muffler 701, igases enter the inlet bushing 751 andpass through the tube section 743 wherein high frequencies, noises, androughness are removed in the spit chamber 746. Additional silencing isaccomplished in chamber 713 las the gases tgo through tube section 711and pass through louvers 712 into chamber. lGases leaving the tube 711enter the crossover chamber 721 and can pass through the neck -719 orthrough an opening formed by an outwardly turned flanged 757 into thechamber 713. Aligned with the opening 757 is a somewhat larger openingprovided by an outwardly turned neck 759 .in the partition 708 so thatit will 'be seen that the lreturn passage .is provided by the volume ofchamber 713 rather than by -a tube as in the previous embodiments. Gasleaving the chamber 713 through opening 759 enters a cross-over chamber761 between partitions 739 and 708 and can then enter the outlet tube715 and be subjected therein to the action of the ispit chambers i717and 726. Low notes in the chamber 761 are subjected to the action of.the tuning tube 741 which connects them to the compound :resonatorformed by the chamber 763 between header 706 and partition 729 which inturn is connected through tuning necks 765 and 749 to the chamber 7167between partitions 729 and 739. It will be noted that cross bleeding toopening 759 is provided through louvers 712 and opening 719 thusenabling -opening 75.7 t-o be reduced in :size over lopening 759 andproviding noise elimination wit-hout an increase in back pressure. Thevolume passage gas iiow between 757 and 759 in combination with theresonators 763 and 767 land the lange size '(high energy absorbing)tuning tube 741 will be especially effective in eliminating theotherwise exceptionally loud torque converter Ipower note.

Each of the ive partitions is provided with drain holes 769 at the topand bottom thereof adjacent the casing 703 :so that water can slosh fromthe end-s of the casing Yto the middle as the muffer .is rocked back andforth by movement of the automobile. The water Within the coolerchambers 763, 767, and 726 can thus 'ow to the chambers 761, 713, 4and721, which are hotter due to the circulation of :gases therethrough, andbe vapor-ized to pass `out of the muffler through tube 715. Directliquid drainage to atmosphere can also be accommodated by a small hole771 at the bottom of the outlet header which is of such a small size asnot to permit lgas leakage, cau-se spitting or hissing, or adverselyaffect the acoustic characteristics lo'f the fnruier. The hole 771 isintended only to let the water leak outwhen the muffler is cold, eig.,when the auto is stopped or just starting and should preferably be nolarger than 1/8" diameter. It could be put in the 4casing wall '703 onthe bottom side of the muiiler.

It will now be recognized that the invention provides many importantimprovements in the muffler eld. Costs of manufacture are reduced by thearrangements of structure which permit subassemblies to be made upoutside of the casing and then inserted as units into the casing. Thevarious pancake designs reduce cost over presently used methods and thecombination of tubes 631 and 636 (FIG. 18) is an important innovationfrom the standpoint of cost reduction and standardization of parts. Avery important feature which should be of great interest to the motoringpublic, as it will double or triple the life of a muffler, is theprovision for inter-chamber drainage whereby the cold water collectingchambers are connected through drain holes in the partitions to the hotgas circulating chambers with the result that the water is vaporized asit sloshes back and forth during motion of the car and does not have anopportunity to eat out the muffler shell or the interior parts. Thisaction can be enhanced by use of a layer of asbestos sheet in the shellconstru-ction, such as disclosed in U.S. Patent No. 2,761,525 andassigned to the assignee hereof, as the asbestos wrapping will cause themufer to run at a higher temperature thereby facilitating vaporization.Also very important is the way the various parts are tied together andto the end headers of the mufers to provide great strength that willresist blow-outs and backres. For example, three different methods ofrigidly supporting the end headers by spot welding at a considerabledistance lengthwise of the muffler away from the plane of the vibration(plane through interlocked joint, eg. 9) are shown, these methods givinga very high resisting moment to bending at the head neck radius andeliminating fatigue failures due to repeated bending. Among otherillustrations, FIG. 1 shows the expanded bushing method; FIG. l0 outletheader shows the drawn head method; and FIG. 13 inlet header shows theinner ange header and bushing method. A further feature adding strengthto the muffler is the use of several spot welded transverse partitions,some of which may be contoured, which not only form acoustic chambersbut brace the oval casings against drumming. The embossments 478 alsohelp to prevent drumming. n

From the operational standpoint, it will be noted that back pressure isat a minimum due to the relatively large gas tubes and cross-overchambers along with arrangements permitting cross-bleeding, especiallycross-bleeding to the outlet tube. The constructions are such as toprovide complete sound elimination for any given application. Severalspit or filter chambers of different volumes are provided to eliminatenoise and roughness over a frequency range from low to high and theharsh bark of modern high compression engines. The resonator chamber andtuning tube arrangements eliminate power notes, second harmonic beatfrequencies, road load harmonics, run down noises, etc. Various featuresprovide for high energy absorption; eg., the large tuning tubes or therestrictor of FIG. 18 and effective sound cancellation will be obtainedin the non-turbulent tri-ow chambers over Wide speed ranges.

It will be recognized that modications may be made in the specicstructures shown herein by way of illustration Without departing fromthe spirit and scope of the invention.

What is claimed is:

1. In an exhaust gas muffler, a casing having a closed end, a rsttransverse apertured partition spaced from the closed end and deningtherewith a first chamber, a second imperforate partition spaced fromthe first and delining therewith a second chamber, a tube extendingthrough said partitions and closed end and opening outside of the casingand having louvers-in the portions thereof within each of said twochambers, and means defining a reverse bend passage surrounding saidlouvers and receiving all gas therefrom, said passage opening into thesecond of said chambers and constituting the only inlet and outlet forit and for the first chamber.

2. The invention set forth in claim 1 wherein said reversed end passageis provided by a pair of mating cavities in complemental pancakestampings spot welded together around a flanged periphery and embracingand spot welded at opposite ends of the tube, said stampings fittingwithin and supported by a'flan'ged slot in the rst partition.

3. In an exhaust gas muffler, a casing, a perforated gas passage tube inthe casing, a combined spit chamber shell and tuning tube member mountedon said tube and surrounding perforations in said tube, said membercomprising complementary halves having flanges secured together along amidplane of the tube, said halves dening an annular spit chamber spacearound the tube extending substantially the full length of the memberand a tuning passage extending substantially normally to said tube andthen turned to extend parallel to said tube and running subst'antiallythe full length of the member, said member including mating flanges onsaid halves secured together to separate the spit chamber space and thetuning passage.

References Cited by the Examiner UNITED STATES PATENTS 2,070,543 2/1937Cary et al. 181-54 2,235,705 3/1941 Haas 181-54 2,580,564 1/1952 Ludlow181-59 X 2,934,161 4/1960 Powers 181-53 RICHARD B. WILKINSON, PrimaryExaminer.

LOUIS I. CAPOZI, Examiner.

R. S. WARD, Assistant Examiner.

1. IN AN EXHAUST GAS MUFFLER, CASING HAVING A CLOSED END, A FIRSTTRANSVERSE APERTURED PARTITION SPACED FROM THE CLOSED END AND DEFININGTHEREWITH A FIRST CHAMBER, A SECOND IMPERFORATED PARTITION SPACED FROMTHE FIRST AND DEFINING THEREWTIH A SECOND CHAMBER, A TUBE EXTENDINGTHROUGH SAID PARTITIONS AND CLOSED END AND OPENING OUTSIDE OF THE CASINGAND HAVING LOUVERS IN THE PORTIONS THEREOF WITHIN EACH OF SAID TWOCHAMBERS, AND MEANS DEFINING A REVERSE BEND PASSAGE SURROUNDING SAIDLOUVERS AND RECEIVING ALL GAS THEREFROM, SAID PASSAGE OPENING INTO THESECOND OF SAID CHAMBERS AND CONSTITUTING THE ONLY INLET AND OUTLET FORIT AND FOR THE FIRST CHAMBER.